This invention relates to the production of epoxy resins. In one aspect, the invention relates to the production of low-chlorine tetrafunctional epoxy resins suitable for electronics applications.
Epoxy resins are used in the electronics inductry for encapsulating semiconductors and other sensitive electronic parts. Encapsulation formulations typically contain an epoxy resin, a curing agent and a filler material such as silica. In the encapsulation process, the electronic part is cast with a molten encapsulation formulation which is then subjected to conditions effective to cure the epoxy resin. The resulting cured resin provides physical integrity and environmental protection for the encapsulated part.
The epoxy resin used in encapsulation formulations must meet a demanding set of criteria, including high glass transition temperature and low chlorine content. Tetrafunctional epoxy resins, such as the reaction products of epichlorohydrin and tetraphenols of ethane, for example, have high Tg and are useful in encapsulation, but these resins typically have residual chlorine levels in excess of 1500 ppm. This residual chlorine can, particularly at the high-temperature conditions which exist in current high-performance electronic systems, corrode metal parts of the underlying electronic component and will cause eventual failure of the part.
It is therefore an object of the invention to provide a process for preparing epoxy resins. In one aspect, it is an object of the invention to prepare low-chlorine tetrafunctional epoxy resins suitable for high-performance electronics applications.